Mobile devices, such as smart phones and tablets, usually have a capacitive touch-sensitive screen to capture interactions made with the user's fingers. Many desktops are equipped with multi-touch hardware. For example, most current Apple Mac™ computers are equipped with a multi-touch-enabled input device of some sort. Multi-touch refers to the ability of a touch-sensing surface (e.g., trackpad or touchscreen) to recognize the presence of two or more points of contact with the surface.